Matthew McConaughey looked like a skeletal shadow of himself jogging outside a gym in Austin, Tex. on Friday. In several layers of workout clothes, the actor, 42, looked alarmingly gaunt and haggard — even more than than he did just five days earlier on a stroll with his mother, Mary.

As previously reported, the usually muscular star's body transformation is all for an important new film role in The Dallas Buyer's Club, which tells the real-life story of Ron Woodruff, a drug addict in 1980s-era Texas who contracts HIV, and became one of the first AIDS activitists.

"I'm playing a guy who was sick and would have loved to have been healthier but wasn't. For me, it's more of a mental thing than a physical thing," McConaughey told Us in August of playing Woodruff, who launched one of the first-ever AIDS support groups.